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IDOT
Dodge Dakota
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2/21/2002
15:38:39
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 Subject: What Gas do you run in your 5.9
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I have a R/T? i just use the lowest kind of gas.. ok i am broke right now do to my last ex-girlfriend.. anywanys? does If i pay for higher octane? does it last longer.. seems like to me that when i fill my tank up with high octane does not last long compare to lower octane? can some one explain to me..
thanx
idoit of the day
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Anthony G
Dodge Dakota
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2/21/2002
16:30:47
|  RE: What Gas do you run in your 5.9
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Simple,
Low octane burns faster or more combustible. The higher the octane the less chance that it will pre ignite the fuel in the cylinder camber while under high pressure. Since your 5.9L has a compression ratio or 8.9:1 that means it doesn't compress the air much verses a higher compression engine or a forced induction engine that forces air into the camber thus creating a 14:1 ration or higher depending on the amount of added boost.
So you will get better gas mileage, better power, and spend less money with 87 or lower octane. You should never have to run anything higher unless you force feed it with a turbo or supercharger or change your head gaskets or heads to increase CR.
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chris
Dodge Dakota
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2/21/2002
16:51:40
| RE: What Gas do you run in your 5.9
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i have a r/t and the dealersip told me to run 93 octane
y is that?
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Anthony G
Dodge Dakota
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2/21/2002
17:06:18
| RE: What Gas do you run in your 5.9
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So did mine, but that was a saleman. He didn't even now what size engine a R/T comes with. If you look threw your paper work, there is a tag that says USE ONLY 87 octane. Trust me, this engine has been around for a long time and it doesn't need premum fuel with only 8:9:1 CR. Even with a slightly modding PCM that the R/T might have over a normal RAM with a 5.9L. If it doesn't ping, it doesn't need higher octane. If it does ping, then you have a belly pan gasket leak or a timing chain slack. The PCM can't tell what fuel you use, there isn't a knock sensor to tell the engine to retard timing that most car have. If you don't need to spend that extra money on fuel. That one main reason I didn't go forced induction yet. I rather spend the money on go fast parts than on wastest fuel money.
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Justin
Dodge Dakota
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2/21/2002
17:28:50
| RE: What Gas do you run in your 5.9
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I have a intake,chip,cam,lifters,rod,rockerarms,headers,punched out cat.
do you think i should be running 87? or 93?
justin?
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Hersbird
Dodge Dakota
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2/21/2002
17:29:21
| RE: What Gas do you run in your 5.9
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Stock R/T's will do the best with 87 octane in both my and the factory's opnion. They even have a TBS describing the shortfalls of using the 89 or 91 where it is not called for. The addition of a MP PCM changes the spark curve and will require the 91, the insturctions with the computer even say so.
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Anthony G
Dodge Dakota
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2/21/2002
17:34:37
| RE: What Gas do you run in your 5.9
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Depends on the chip type and maker. Anything other than Mopar or maybe ASE. Take it off and save your self the money.
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Justin
Dodge Dakota
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2/21/2002
17:36:53
| RE: What Gas do you run in your 5.9
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ok. ya i dunno
your making sence and seem that you know alot.
but ship my r/t seems alot faster with 93
but----
!!!!!!!!!!! 87 = cheaper !!!!!!!!!!!!!!
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Justin
Dodge Dakota
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2/21/2002
17:42:15
| RE: What Gas do you run in your 5.9
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i just use MOPAR !!!!!!!!!
thats all i trusted
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Todd
Dodge Dakota
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2/21/2002
19:45:41
| RE: What Gas do you run in your 5.9
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I just got a 99 rt about 4 months ago,after a short time,I noticed some ping,I thought at the time it may have been just after a fill up with 87 octane,so since I have been using higher octane,and the ping is there,but not as bad.My question is this:Is it possible for that ping to be coming from a loose exhaust,or clamp?It definately sounds as if it is coming from the bottom,and reflecting off the ground,I thought that perhaps the previous owner may have swapped the exhaust back to factory before trading it in.If not,where should I begin to make the ping dissappear,timing?
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MikeD
Dodge Dakota
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2/21/2002
20:52:19
| RE: What Gas do you run in your 5.9
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I think the bigger more high performance engines need the higher octane to perform at its best. The 87 octane thats stated in the book is probably for the most common engines like the 2.5,3.9,&4.7 I've used 93 octane in my R/T and haven't had any ping but since gas is gettin expensive I've back off to 90 and its still doing good. I used the middle octane in my old 87 stang GT for awhile and noticed a ping but once I switched back to 93 after a few tanks the pinging went away. So I think the pinging has alot to do w/ what type of octane you use.
~Mike~
'01 RC R/T
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Anthony G
Dodge Dakota
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2/22/2002
10:06:30
| RE: What Gas do you run in your 5.9
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If you hear a clacking noise while your engine is under load (accelerating), then it's pinging. If you hear a rattle in neutral when revving your engine then it could be a bad cat or loose exhaust. Todd, just take the time and remove you Throttle body hat and open up the TB blades while looking into your intake with a flashlight and check for oil on the pan, make sure you don't have a oil puddle in the back. If you do, then that's your problem with pinging. Not the gas you use. Check you plugs too.
Mike, engine size had nothing to do with what type of fuel you need. It all comes down to the cylinder chamber setup. If you haven't changed any internal part or aftermarket PCM, I really think your engine would run better with lower octane. Maybe because you feed your beast 90-93 octane it's learn to make the best of it, try resetting(unplug battery+turn on ignition) your system then run 87 for 50-100miles then come back at tell me it doesn't like it.
CR: How Much the air gets compressed, the higher the more unstable it gets or better chance it will pre-detonate or ping. But more power, because compressed air explodes with more energy.
Fuel: Higher is not better, the higher the octane the more diluted. It's like adding water to you your Valka, it will not help power. Unless you need a diluted gas because your engine is pre-detonating. All it means is, it's a more stable fuel that was made for any engine has a high CR factor. Like LT1 Corvette Race version with 11:1 CR or Forced Induction Vehicle.
Spark: Used to ignite the fuel and air, a colder plug can help prevent ping.
Timing: Determents where and when it should ignite the charged air and gas.
Air: Colder is more dense thus having more to compress to make energy to push the crank. Making power. Hotter the less dense, or humid when water molecules take the place or air.
Final words, do what you wish or think is better. But with my heavy foot, I only get 13.2MPG. But I do WOT with that puppy every day a few times a day. :) So every penny counts.
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kota on 20s
GenIII
2/22/2002
12:39:15
| RE: What Gas do you run in your 5.9
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MikeD, if you truck has a slight ping, try replacing the thermostat with a 180 degree one, and change the plugs to autolight copper 3923's. your truck should never ping again with 87 oct.
Eric
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Hersbird
Dodge Dakota
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2/22/2002
13:11:57
| RE: What Gas do you run in your 5.9
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I use the 87 in my 200 R/T and have never heard any ping. It is completely stock and I know what the pinging sounds like. On my 93 5.2 it got pinging good after the MP PCM swap and you had to use 91 or higher. I always described it as sounding more like a deisel rattle then a ping. Some people may be getting pinging as the mileage gets up on their motors as carbon builds up and increases compression and builds hot spots.
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kota on 20s
GenIII
2/22/2002
16:46:32
| RE: What Gas do you run in your 5.9
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hey hersbird, how did you like the pcm on your 5.2? i have to get leach to flash mine because they dont have one for the 5speeds.
do you think its worth $400?
Eric
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Hersbird
Dodge Dakota
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2/22/2002
17:12:27
| RE: What Gas do you run in your 5.9
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That MP PCM was really the only mod I spent any money on for my 93 and it (along with the free stuff) picked up 1 sec in the 1/4. I ran a 15.9 bone stock and a 14.9 with the mods. Without the computer it would rap up against the RPM limiter before shifting and cut out a couple of times before finally shifting (the best I could get was 15.4 1/4's). It solved that instantly. The free stuff (or damn close to free)I did to help the computer work well, was a short belt, removed the exhaust system behind the cat, a round K&N (the 93's had round aircleaners), accel coil, MSD wires, removed the tailgate, bumper, and spair, and installed some old 225/65/15's on the rear (a little better final drive ratio then the stock 225/75/15). It was a RC LE 5.2 auto, with 3.55 LS. It got no traction after those mods and I had to pretty much idle it off the line (I'm sure tires would have been the next step, but back than nobody was making wide wheels for the 6x4.5 lug pattern. I used to commute 50 miles a day in bay aera traffic so I would swap the PCM back and forth depending on weather or not I was commuting or racing at Sears Point. The PCM was easilly the best $250 (at that time) I could have spent on the truck. I'd say it was good for a .5 sec with those mods and would have been even better with more traction which suddenly became the #1 problem.
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kota on 20s
GenIII
2/22/2002
17:21:47
| RE: What Gas do you run in your 5.9
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so do you think its worth $400?
Eric
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kota on 20s
GenIII
2/22/2002
17:23:08
| RE: What Gas do you run in your 5.9
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keep in mind, that im getting it flashed, so i cant take it out and change it if i wanted.
if you were in this situation would you flash it?
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Hersbird
Dodge Dakota
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2/23/2002
00:41:45
| RE: What Gas do you run in your 5.9
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I don't think the flashed PCMs come close to performing like a MP PCM from what I understand. Maybe if you really got a lot of mods and the stock PCM just can no longer handle the job. So they don't make a PCM for the 99 5-speeds? I don't think just a flash with mild mods would be worth $400. That much money buys something sweet like 1.7 rockers, an M1, a cam, or head porting which would certainly give more then a flash PCM.
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kota on 20s
GenIII
2/23/2002
01:15:57
| RE: What Gas do you run in your 5.9
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well, mike leach is the one who did the pcm's for mopar. he said i could even add more timing than the mopars have since he does the flashing. so it would give more power than the mopars.
so far the mods i have are as follows:
k&n gen II
50mm TB
M-1 manifold (not installed yet)
1.7RR's
jba headers
carsound cat
dumped gibson
i dont want a cam because i dont think it will pass smog in cali.
so do you think it would be worth the cash?
Eric
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Hersbird
Dodge Dakota
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2/23/2002
01:37:18
| RE: What Gas do you run in your 5.9
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I have heard good things about Leach flashing the 4.7 computers so maybe he can make it worth the $400 as you already have everything but heads, and you might as well no port the stockers but switch to the MP R/T heads and then you'll really need the flash anyway. I see now they stopped making the MP computer for the 5 speed 5.2's in 97, I wonder whats so different about the 98's and 99's? Leach is a really good Mopar guy who knows far more then me about it, so if he says it'll work then I trust him. Some of these other companies like Jet really just try to apply what worked on the Chevies to our Dodges and they never get it right. Leach has been doing Magnum Dodge stuff from the start so he'll get it set right for the mods. Can he raise or remove the speed limiter? you might start pushing that in the 1/4 mile if it's 98mph.
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kota on 20s
GenIII
2/23/2002
01:46:07
| RE: What Gas do you run in your 5.9
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yea he said he could raise the revlimiter to 9000rpm if i wanted. ill just go with 6000rpm, and on my 98 the speed limiter is at 115, but he raises that to 225mph.
i love people who i meet on the street who say "yea i have the TB spacer and the jet II chip, and it got me an extra 40hp" YEA...RIGHT!
if i do anything to the pcm, leach is the only guy that will touch it
Eric
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MikeD
Dodge Dakota
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2/23/2002
02:09:57
| RE: What Gas do you run in your 5.9
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Well Mike Leach recommended B&G Chrysler for us unfortunate 2001 and up guys. I really wanted Leach to do mine too I was kinda bummed when he said he wouldn't be gettin any power tables for ours. If he recommends this place then I'm sure they have to be good.
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HSKR
Dodge Dakota
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2/23/2002
17:50:53
| RE: What Gas do you run in your 5.9
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I run 89 in my R/T with the Mopar PCM. It runs better on the 89 than the 91 I was running for a while. Havn't tried any 87 due to the fat that I do have the performace PCM installed.
So higher octane is not required with the Mopar PCM, at least not 93.
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HSKR
Dodge Dakota
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2/24/2002
01:25:41
| RE: What Gas do you run in your 5.9
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kota, You can get a cam and it will pass emissions as long as you get a custom grind to pass emissions.
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kota on 20s
GenIII
2/24/2002
01:29:59
| RE: What Gas do you run in your 5.9
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really? just a couple of questions
1) if it will pass emissoions, will it give me any decent hp?
2) do you think i can get one that will work with my 1.7RR's?
3) where should i look for a custom grind?
Eric
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HSKR
Dodge Dakota
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2/25/2002
01:31:39
| RE: What Gas do you run in your 5.9
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I'm not real versed on cams. I would say to contact Comp Cams, or some other cam grinder and ask them. They should be able to make one for you that will pass emission, will give a good increase in performance, and will work with the 1.7's.
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Tom Perso
Dodge Dakota
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2/25/2002
02:27:37
| RE: What Gas do you run in your 5.9
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The higher octane is needed with R/T's and most performance computers since the ignition timing is advanced. That will give you more power, but just by advancing the ignition, you need to slow the burn down, so higher octane is needed.
The only reason they will run with lower octane gas is because of the knock sensor on the motor... it detects knock and reduces the timing.
The performance computer is a cheap way to get more power out of a stock motor.
You want power? Get a lumpier cam (more duration/lift) and bump the C/R. With more overlap, you get higher RPM scavanging in the combustion chamber, so upper RPM power is increased, but also losing lower end.
You can safely bump the C/R with a bigger cam since the "dynamic" compression is about the same as a stock cam due to the greater overlap of the performance cam. This is a GROSS over-slimplication of the therory, but you can get the idea. It's all in what you want to do.
I'm going thru this right now with building a Hi-Po Porsche 914 motor for a Bug. With a nice, lumpy cam, you can run higher C/R's and still run pump gas - And still make power...
Also, remember. By advancing timing, you are creating more negative work on the motor (since the burn is happening earlier), but a hotter explosion. It's a trade-off. Getting quick-burn combustion chambers will allow less final ignition timing for less negative work and good combustion.
If you have a set of matched heads and pistons, you can pump gas on 12:1 compression (!!!) on a VW. Due to the high swirl and fast burn combustion chambers... Yes, we are talking VW's here, but they are all four cycle Otto process motors. It all applies, just the numbers are different... :)
Running higher octane gas on a stock motor gets you nowhere except a lighter wallet. If it's pinging, new plugs and wires (relocated as well for less cross-fire) should clear things up.
Hope this helps,
Tom Perso
http://www.qtm.net/~persoj
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HSKR
Dodge Dakota
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2/25/2002
10:42:12
| RE: What Gas do you run in your 5.9
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Sorry to tell you, but no knock sensors on Dakota's!!! And you don't HAVE to run high octane with R/T even with the Performance computer. Run whatever is safe in your vehicle. I run 89 no problems, and have never knocked. I have the mOpar PCM on my R/T as well. And just two weeks ago on the dyno I put out 251hp on 89 octane gas with 95K miles on my engine.
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MikeD
Dodge Dakota
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2/25/2002
11:08:55
| RE: What Gas do you run in your 5.9
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HSKR, what mods do you have on your R/T?
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Hersbird
Dodge Dakota
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2/25/2002
11:47:56
| RE: What Gas do you run in your 5.9
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Dude, I can't beleive you're about to turn 100 (100K miles that is)! Modded and run hard at times, and people try and say the Dakota is unrelaible. I'm sure you have broke some stuff along the way, right? I agree about the knock sensor thing, my R/T doesn't have any. The factory puts knock sensors on cars that need them, stuff that has potential to knock with lower grade feuls. A stock R/T should not knock even with 87 octain feul. I believe my DOHC neon did have a knock sensor and although the factory recommended 91 octain to achive 150 HP it could run 87 octain and it would just cut back timing some and give more like 140 HP. I think this is what Tom is talking about, but it doesn't apply to the Dakotas.
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